Medical Health Encyclopedia

Porphyrins - urine

How the test will feel:

The test will feel the same as normal urination.

Why the test is performed:

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This test is most often performed when porphyria or other disorders that can cause abnormal urine porphyrins is suspected.

The most important function of porphyrins is as components of heme. Heme is made from iron + protoporphyrin. Hemoglobin is made up of four heme molecules + four globin proteins. Oxygen binds to the iron in the heme molecules.

Various kinds of porphyrins exist with the same basic structure, but with slightly different chemical appearance.

Heme production involves biochemical conversion of porphyrins into delta-ALA, then to PBG, then uroporphyrin, then coproporphyrin, then protoporphyrin, and finally into the end product -- heme.

Each of these steps requires the presence of a specific enzyme. If any of the enzymes are deficient (because of a genetic disease or interference by a toxic substance), the intermediate substances build up, and a type of porphyria results.

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